Page 125 - ICSE Chemistry 6

3. John Dalton is credited for proposing the modern atomic theory.
4. Fungicides are chemicals which provide nutrients required by the crops for proper growth.
5. Chemistry plays a signifi cant role in the development of cosme cs.
6. Noble gases do not react chemically with elements.
7. Silver and gold are widely used in construc on of buildings.
8. Filtra on is used to separate a soluble solid and a liquid.
9. Evapora on is used to separate homogeneous solid-liquid mixtures like extrac ng salt from sea
water.
10. In a mixture of iron and sulphur, iron is separated by rolling a magnet over the mixture.
11. The par cles of ma er move around in the space that they occupy.

12. A molecule does not have an independent existence.
13. The molecules are closely packed in solids and the intermolecular forces are the strongest.
14. Gases have very high density.
15. A chemical change can be caused by hea ng a substance.
16. Groundwater is purer as it gets fi ltered through many layers of sand, rocks and soil.
17. Ice being heavier than water fl oats in liquid water.
18. S rring the solu on increases the solubility of the solute in the solvent.

19. The forma on of a solu on is a chemical change.
20. Reverse osmosis is a method of water purifi ca on in which water is forced out of the waste through
a semipermeable membrane by applying pressure.
21. Air is not represented by any chemical formula whereas compounds have defi nite formulae.
22. Water vapour are formed due to evapora on and boiling of water.
23. CNG is used as a fuel in power sta ons, houses, industries and steam engines.
24. The atmosphere plays a very important role in regula ng the temperature on the surface of the earth.
25. Air pollu on can damage crops and/or aff ect their growth.

C. Answer in short.
1. Which are the two main branches of science?

2. What is alchemy?
3. Who formulated the ‘modern periodic table of elements’?
4. What are preserva ves?
5. What is the use of ampicillin?
6. What is the diff erence between pure and impure substances?
7. Defi ne symbol of an element. What does it represent?
8. What is electrolysis?
9. What is a chemical bond?
10. State the principle of separa on.

11. What is ma er?
12. How is an atom diff erent from a molecule?
13. Why are liquids free fl owing?
14. Why do gases diff use very rapidly?

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